8335766: Switch case with pattern matching and guard clause compiles inconsistently

[lahodaj]

Hi all,

This pull request contains a backport of commit 537d20af from the openjdk/jdk repository.

The commit being backported was authored by Jan Lahoda on 10 Jul 2024 and was reviewed by Aggelos Biboudis.

Thanks!

Original description:
When javac parser see a case label, it needs to disambiguate between expressions (constant labels) and patterns. But, for code like:

case R(int x) when (x > 0)

the parser will try to parse the label as an expression, which is obviously not correct. The problem is that it does not disambiguate before when, and there indeed is an expression after when.

The proposal is to disambiguate as a pattern once there is when after a closing parenthesis at the top-level. This should prevent the code to even look at the when expression

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8335766: Switch case with pattern matching and guard clause compiles inconsistently (Bug - P4)

Reviewers

• Vicente Romero (@vicente-romero-oracle - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/20111/head:pull/20111
$ git checkout pull/20111

Update a local copy of the PR:
$ git checkout pull/20111
$ git pull https://git.openjdk.org/jdk.git pull/20111/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 20111

View PR using the GUI difftool:
$ git pr show -t 20111

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/20111.diff

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[bridgekeeper]

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[openjdk]

@lahodaj This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8335766: Switch case with pattern matching and guard clause compiles inconsistently

Reviewed-by: vromero

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At the time when this comment was updated there had been 1 new commit pushed to the jdk23 branch:

• 5b9ecb1: 8333886: Explicitly specify that asSlice and reinterpret return a memory segment backed by the same region of memory.

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[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

@lahodaj The following label will be automatically applied to this pull request:

• compiler

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[mlbridge]

Webrevs

• 00: Full (2aae13c4)

[vicente-romero-oracle]

lgtm

[lahodaj]

/integrate

[openjdk]

Going to push as commit e991c0f.
Since your change was applied there have been 3 commits pushed to the jdk23 branch:

• 6720685: 8335966: Remove incorrect problem listing of java/lang/instrument/NativeMethodPrefixAgent.java in ProblemList-Virtual.txt
• 4aab58b: 8335637: Add explicit non-null return value expectations to Object.toString()
• 5b9ecb1: 8333886: Explicitly specify that asSlice and reinterpret return a memory segment backed by the same region of memory.

Your commit was automatically rebased without conflicts.

[openjdk]

@lahodaj Pushed as commit e991c0f.

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